Notice that the days of sacrifice are not over. We are to present our bodies a living sacrifice. Sacrificing has been transferred from the physical slaughtering of animals to the sacrifice of the self, from the slaying of a dumb and uncomprehending beast to the intelligent and deliberate choice of an understanding human, made in the image of God.
The principles of the sacrifices given in Leviticus 1-5 and so forth still apply to us under the New Covenant in their spirit—the stretching out of principles to their spiritual intent. It is these principles that Paul is drawing on for this command. We are to present our lives as a sacrifice to God.
Remember, our salvation rests on the human sacrifice of Jesus Christ of Nazareth. First, He gave up His glory to become a man. Second, He sacrificed His life; for 33 ½ years, He laid it down as an offering to God, and as an example to us of perfect obedience. Finally, He gave up His human life as a sacrifice on the stake.
Sacrifice is a New Testament doctrine! It is on such a higher plane that there is no comparison with the sacrificing done in the Old Testament. Now we have to be sacrificed and much in the same way, in principle, that Christ was. Many individual verses or paragraphs in the Bible explain that such things as prayer, thanksgiving, faith, and repentance are Christian sacrifices.